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IP Alert: No Foreseeability Exception to the Doctrine of Equivalents

February 21, 2014

On February 19, 2014, the Court of Appeals for the Federal Circuit held in Ring & Pinion Service Inc. v. ARB Corp. that there is not, and has never been, a “foreseeability limitation” on the application of the doctrine of equivalents. This case is significant in that it clarifies earlier Federal Circuit holdings that addressed the issue of “foreseeability” under the doctrine of equivalents.

The doctrine of equivalents is a form of infringement that a patentee may assert in the absence of literal infringement. Generally, and subject to numerous limitations and qualifications, the doctrine of equivalents allows a patentee to assert infringement where an absent limitation in the accused device or method performs substantially the same function in substantially the same way to accomplish substantially the same result as is claimed. In an earlier case, Sage Products, Inc. v. Devon Industries, Inc., the Federal Circuit rejected the patentee’s attempt to assert the doctrine of equivalents where the alleged infringement had been foreseeable at the time of filing, holding that “as between the patentee who had a clear opportunity to negotiate broader claims but did not do so, and the public at large, it is the patentee who must bear the cost of its failure to seek protection for this foreseeable alteration of its claimed structure.” Some have questioned whether the Sage Products opinion provides a bar to the assertion of the doctrine of equivalents where the absent claim limitation was foreseeable.

The Federal Circuit answered this question in the negative in Ring & Pinion. Ring & Pinion (“R&P”) sought declaratory judgment that its “Ziplocker” product did not infringe ARB’s patent, U.S. Patent No. 5,591,098 (“the ’098 patent”). The patent concerns an improved automobile locking differential. The parties stipulated that R&P’s Ziplocker product literally met every limitation of the asserted claims except one, a “cylinder means.” The parties further agreed that the Ziplocker product included a structure equivalent to the “cylinder means,” and that this equivalent structure would have been foreseeable to a person having ordinary skill in the art at the time the application for the ’098 patent was filed. Thus, the only question before the district court was the legal issue of whether the equivalent structure could be covered under the doctrine of equivalents even though the structure was foreseeable at the time of the patent application. The district court held there was no such bar, but still entered a finding of non-infringement based upon the doctrine of claim vitiation. Claim vitiation, another limitation on the doctrine of equivalents, applies where a finding of infringement under the doctrine of equivalents would write an express limitation out of claim.

On appeal, the Federal Circuit agreed that there is no foreseeability bar to the doctrine of equivalents. Relying on U.S. Supreme Court precedent dating to 1950, the court stated that, to the contrary, “known interchangeability” of structures weighs in favor of finding infringement under the doctrine of equivalents. The court also emphasized that there is no foreseeability limitation on the doctrine of equivalents for means-plus-function claims, rejecting R&P’s argument that Sage Products created a general bar to equivalents. Rather, the court distinguished Sage Products as involving the doctrine of claim vitiation, holding that the scope of the claim in Sage Products was “limited in a way that plainly and necessarily excluded a structural feature that was the opposite of the one recited in the claim.”  

The claim limitation at issue was a mean-plus-function limitation. R&P argued that another earlier Federal Circuit case, Chiuminatta Concrete Concepts, Inc. v. Cardinal Industries, Inc., had created a bar to the application of equivalents of a means-plus-function claim where the alleged equivalent had been foreseeable. The court rejected this assertion. After explaining the timing and functional differences between means-plus-function claims and the doctrine of equivalents, the court held that “when the accused technology was known at the time of patenting and the functions are identical, the structural equivalence inquiry under § 112 and the structural equivalence portion of the doctrine of equivalents are coextensive.” As a consequence, the court held that there was likewise no foreseeability bar in these circumstances for the mean-plus-function claim limitation at issue.

Based on the above analysis, the court held that a finding of infringement was proper in light of the parties’ stipulation that all elements were met by the accused device, either literally or under the doctrine of equivalents. The court then held that the stipulation of fact entered into by the parties was fair and the district court was bound to enforce it. Further, held the court, the stipulation precluded the conclusion that the cylinder limitation was in some way vitiated since the parties stipulated to its equivalence. Thus, the court reversed the district court’s ultimate finding of non-infringement, and remanded for entry of a judgment of infringement.

This pro-patentee Federal Circuit opinion is significant for patent litigants in cases where the doctrine of equivalents is at issue. For more information, please contact Fitch Even partner Allen E. Hoover

Written by Fitch Even attorney Nicole L. Little


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